Finding Things in Complex Environments

Have you ever looked for something in a teenager's bedroom? Tough, isn't it? Everyday experience tells us that when the background is cluttered, it's harder to find an object. But how should we define "complexity" and can we apply the same concepts to other animals?

In the Leigh Woods nature reserve, on the other side of the famous Clifton Suspension Bridge from Bristol, they pinned identical artificial ‘moths’ to different trees.

The ‘moths’ were made of coloured paper that matched the average colour of the trees in the woodland and so were quite hard to spot. Being identical, the difficulty of finding these artificial prey varied only with the bark of the tree they were pinned to.

For birds, there was a dead mealworm under each paper triangle – the researchers checked the prey regularly and if the mealworm had gone then they knew that birds had spotted the prey.

To determine humans’ ability to find the targets, they got volunteers to walk, separately and slowly, along the meandering path through the woods, searching for the paper triangles.